;; outdated

(defun ev3-forward-dec ()
  (interactive)
  (set-motor-both (get-speed-forward-dec) ))

(defun ev3-reverse-dec ()
  (interactive)
  (set-motor-both (get-speed-reverse-dec) ))

(defun already-rotates-opposite-reset (way)
  (let ((reset-speed 100))
    (when (rotates-p way)
      reset-speed) ))

;; works

(defun color-stop-on-color (&optional col)
  (or col (setq col (color-number "none")))
  (when (and (= col (color-get-color))
             (moving-forward-p) )
    (ev3-stop)
    (ev3-reverse-inc)
    (sleep-for 0 200) ))

;; doesn't work for perhaps several reasons

(let ((color-stop-on-color-timer))
  (defun color-stop-on-color-enable ()
    (interactive)
    (let ((how-often-secs 1))
      (setq color-stop-on-color-timer
        (run-with-idle-timer how-often-secs t #'color-stop-on-color) )))
  (declare-function color-stop-on-color-enable nil)

  (defun color-stop-on-color-disable ()
    (interactive)
    (cancel-timer color-stop-on-color-timer) )
  (declare-function color-stop-on-color-disable nil) )